I tested again.
It was liftoff, liftoff not show the upvote arrow highlights after you refreshing.
The score (add by upvote) is still count the first time. lemmy.world store my vote correctly. Only liftoff not show the highlight up arrow when I refreshing.
If I press up again in post I upvoted before, score not go up.
If I press down in post I upvoted before, score go down by 2 (my upvote is delete, then add my downvote).
So, Lemmy instance register my vote correctly